With the development of communication technology, an antenna array is used for transmitting data. As the technology development, an antenna array is used in a LTE technology. For example, a diversity communication or a multiplexing communication can be used for the antenna array in the LTE technology.
In an antenna array, the number of the antennas might be larger than 100. The communication of the antenna array may be performed under a frequency division duplexing (FDD) mode or a time division duplexing (TDD) mode. In FDD mode, the feedback loading is large due to the large number of the antennas. It is needed to reduce the overhead loading when the antenna array is performed in FDD mode.